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:mod:`trace` --- Trace or track Python statement execution
==========================================================
.. module:: trace
:synopsis: Trace or track Python statement execution.
The :mod:`trace` module allows you to trace program execution, generate
annotated statement coverage listings, print caller/callee relationships and
list functions executed during a program run. It can be used in another program
or from the command line.
.. _trace-cli:
Command Line Usage
------------------
The :mod:`trace` module can be invoked from the command line. It can be as
simple as ::
python -m trace --count -C . somefile.py ...
The above will execute :file:`somefile.py` and generate annotated listings of all
Python modules imported during the execution into the current directory.
Meta-options
^^^^^^^^^^^^
``--help``
Display usage and exit.
``--version``
Display the version of the module and exit.
Main options
^^^^^^^^^^^^
The ``--listfuncs`` option is mutually exclusive with the ``--trace`` and
``--count`` options . When ``--listfuncs`` is provided, neither ``--counts``
nor ``--trace`` are accepted, and vice versa.
``--count, -c``
Produce a set of annotated listing files upon program completion that shows
how many times each statement was executed.
See also ``--coverdir``, ``--file``, ``--no-report`` below.
``--trace, -t``
Display lines as they are executed.
``--listfuncs, -l``
Display the functions executed by running the program.
``--report, -r``
Produce an annotated list from an earlier program run that used the ``--count``
and ``--file`` option. Do not execute any code.
``--trackcalls, -T``
Display the calling relationships exposed by running the program.
Modifiers
^^^^^^^^^
``--file=<file>, -f``
Name of a file to accumulate counts over several tracing runs. Should be used
with the ``--count`` option.
``--coverdir=<dir>, -C``
Directory where the report files go. The coverage report for
``package.module`` is written to file ``dir/package/module.cover``.
``--missing, -m``
When generating annotated listings, mark lines which were not executed with
'``>>>>>>``'.
``--summary, -s``
When using ``--count`` or ``--report``, write a brief summary to
stdout for each file processed.
``--no-report, -R``
Do not generate annotated listings. This is useful if you intend to make
several runs with ``--count`` then produce a single set of annotated
listings at the end.
``--timing, -g``
Prefix each line with the time since the program started. Only used while
tracing.
Filters
^^^^^^^
These options may be repeated multiple times.
``--ignore-module=<mod>``
Accepts comma separated list of module names. Ignore each of the named
modules and its submodules (if it is a package).
``--ignore-dir=<dir>``
Ignore all modules and packages in the named directory and subdirectories
(multiple directories can be joined by ``os.pathsep``).
.. _trace-api:
Programming Interface
---------------------
.. class:: Trace(count=1, trace=1, countfuncs=0, countcallers=0, ignoremods=(), ignoredirs=(), infile=None, outfile=None, timing=False)
Create an object to trace execution of a single statement or expression. All
parameters are optional. *count* enables counting of line numbers. *trace*
enables line execution tracing. *countfuncs* enables listing of the functions
called during the run. *countcallers* enables call relationship tracking.
*ignoremods* is a list of modules or packages to ignore. *ignoredirs* is a list
of directories whose modules or packages should be ignored. *infile* is the
name of the file from which to read stored count information. *outfile* is
the name of the file in which to write updated count information. *timing*
enables a timestamp relative to when tracing was started to be displayed.
.. method:: Trace.run(cmd)
Run *cmd* under control of the :class:`Trace` object with the current tracing parameters.
*cmd* must be a string or code object, suitable for passing into :func:`exec`.
.. method:: Trace.runctx(cmd, globals=None, locals=None)
Run *cmd* under control of the :class:`Trace` object with the current tracing parameters
in the defined global and local environments. If not defined, *globals* and
*locals* default to empty dictionaries.
.. method:: Trace.runfunc(func, *args, **kwds)
Call *func* with the given arguments under control of the :class:`Trace` object
with the current tracing parameters.
.. method:: Trace.results()
Return a :class:`CoverageResults` object that contains the cumulative results
of all previous calls to ``run``, ``runctx`` and ``runfunc`` for the given
:class:`Trace` instance. Does not reset the accumulated trace results.
.. class:: CoverageResults
A container for coverage results, created by :meth:`Trace.results`. Should not
be created directly by the user.
.. method:: CoverageResults.update(other)
Merge in data from another :class:`CoverageResults` object.
.. method:: CoverageResults.write_results(show_missing=True, summary=False, coverdir=None)
Write coverage results. Set *show_missing* to show lines that had no hits.
Set *summary* to include in the output the coverage summary per module. *coverdir*
specifies the directory into which the coverage result files will be output.
If ``None``, the results for each source file are placed in its directory.
..
A simple example demonstrating the use of the programming interface::
import sys
import trace
# create a Trace object, telling it what to ignore, and whether to
# do tracing or line-counting or both.
tracer = trace.Trace(
ignoredirs=[sys.prefix, sys.exec_prefix],
trace=0,
count=1)
# run the new command using the given tracer
tracer.run('main()')
# make a report, placing output in /tmp
r = tracer.results()
r.write_results(show_missing=True, coverdir="/tmp")
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